Changes between Version 17 and Version 18 of AccretionDiskTutorial
- Timestamp:
- 08/28/12 13:34:33 (12 years ago)
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AccretionDiskTutorial
v17 v18 1 1 = Setting up an accretion disk simulation in Astrobear 2.0 = 2 2 3 === Modules and Files === 3 This tutorial is designed to teach you the essential knowledge needed to set up a Disk module in AstroBEAR 2.0 4 [[BR]] 5 6 == Modules and Files == 4 7 5 8 These directions assume that you are able to compile a problem, in case you have never compiled AstroBEAR check the page [https://clover.pas.rochester.edu/trac/astrobear/wiki/BuildingAstroBear How to Build AstroBEAR 2.0] [[BR]] … … 15 18 '''Warning: ''' It is good practice to delete ''profile.data'' from the problem folder before executing AstroBEAR for the first time, failure to do so will likely result in execution errors. 16 19 17 == = Getting familiar with the module ===20 == Getting familiar with the module == 18 21 19 22 After checking that the disk module compiles and runs without any issues, you can examine the chombo files created by the first run of this module.[[BR]][[BR]] … … 30 33 - PointGravity: a point mass located at the center of the disk 31 34 35 '''Note''': Numerical values reported by Visit are in computational units, ''scales.data'' contains the scales values needed to translate computational units to physical units. 32 36 33 == = Initial Conditions ===37 == Initial Conditions == 34 38 35 39 Now you can proceed to examine ''problem.data'' contained in the '''BasicDisk''' folder. 36 The default problem.data file contains a n array of fieldthat can be changed depending on the user's needs, let's analyze some of them40 The default problem.data file contains a list of initial conditions that can be changed depending on the user's needs, let's analyze some of them 37 41 38 42 || ddensity=1d0 || disk density || … … 43 47 || height=5e9 ||disk height|| 44 48 || mass=.6d-1 ||central particle mass|| 49 50 '''Note:''' for this specific module, problem.data no scaling operation is required from the user 45 51 46 52 Sometimes it can be useful to change the size of the physical boundaries of the simulation, this can be done by modifying the section below contained in ''global.data'' … … 54 60 }}} 55 61 56 == = Scales ===62 == Scales == 57 63 58 Scales are parameters that can actively affect the outcome of a simulation.[[BR]]64 AstroBEAR makes use of scales to adapt physical values to a numerical simulation, scales can affect the behavior of a model [[BR]] 59 65 Physics.data contains a section dedicated to the setting of scales: 60 66 … … 68 74 }}} 69 75 70 It is good practice to adapt the scales to the specific needs of a simulation, let's see an example:[[BR]] 71 In the code listed in the Initial Conditions section we set the disk radius to be 2e10cm, with that, we set our length scale parameter (lScale) to be .5e10cm[[BR]] 72 this will result in R,,disk,,/lScale = 4. 76 In the values listed above the disk radius is set to 2e10cm, with that, we set our length scale parameter (lScale) to be .5e10cm[[BR]] 77 the resulting ratio R,,disk,,/lScale is 4.[[BR]] 78 For convenience purposes, a rule of thumb is to keep the R,,disk,,/lScale within about one order of magnitude from the value above:[[BR]] 79 for example, if we had 2e15 as R,,disk,, a good lScale would be .5e15 or 1e15. 73 80 74 '''Warning:''' Always make sure to check ''physics.data'' for the entries81 '''Warning:''' Always make sure to check ''physics.data'' for 75 82 {{{ 76 83 MinTemp = 1e-3, ! minimum allowed temperature for the system, without cooling, this should be zero. … … 80 87 81 88 82 == = Softening ===89 == Softening == 83 90 84 91 Softening is a numerical trick commonly used in simulations to prevent divergences when a value comes close to another and the force of gravity goes to infinity.[[BR]] … … 104 111 '''Warning: ''' It is good practice to keep the soft_radius between .1 and .3. Failure to do so may result in undesired outcomes. 105 112 106 == = Fixed grid to AMR ===113 == AMR == 107 114 108 115 The resolution of the simulation can be changed by modifying the following fields contained in [https://clover.pas.rochester.edu/trac/astrobear/wiki/GlobalDataExplained global.data]: … … 148 155 [[BR]] 149 156 150 == = Mach Number ===157 == Mach Number == 151 158 152 159 When setting up a new simulation it is good practice to check that the Mach values are below a certain threshold, in most of computational simulation this value is ~60. [[BR]] Values above this threshold may create difficulties in evolving a model and therefore create computational errors. … … 156 163 [[Image(mach.png, 500px)]] 157 164 158 == = Other parameters ===165 == Other parameters == 159 166 160 167 Now that you have acquired the essential knowledge to set up a disk module, you should be capable to change other aspects of a simulation such as:[[BR]]
